1. Field of the Invention
The present invention relates to working depth adjusting devices that are mounted to rotary tools, such as screwdrivers and drills, in order to adjust a working depth e.g., a driving depth of screws and a depth of drilled holes.
2. Description of the Related Art
In general, a driving depth adjusting device is mounted to a front portion of a screwdriver and is operable to adjust a driving depth of screws into a workpiece. A driver bit is mounted within the adjusting device and extends forwardly from the adjusting device. Therefore, in order to change a driver bit to another driver bit, it is necessary to remove the adjusting device from the screwdriver.
Japanese Utility Model Registration No. 2510156 and U.S. Pat. No. 6,758,116 teach driving depth adjusting devices that can be removed from a tool body of a screwdriver.
According to Japanese Utility Model Registration No. 2510156, a driving depth adjusting device includes an operation sleeve operable for adjusting a driving depth. The operation sleeve is attached to the front portion of a tool body of a screwdriver by means of a threaded portion provided on the operation sleeve and a corresponding thread portion provided on the front portion of the tool body. Rotating the operation sleeve changes the distance between the operation sleeve and the front portion of the tool body, so that an extending distance of a driver bit from the operation sleeve can be changed in order to adjust the driving depth. In addition, the operation sleeve can be removed from the tool body by rotating the operation sleeve in order to completely disengage the threaded portion of the operation sleeve from the thread portion of the tool body.
According to U.S. Pat. No. 6,758,116, a driving depth adjusting device has resilient hinges with engaging tabs that can engage a tool body. In order to remove the adjusting device from the tool body, the resilient hinges can be deformed to disengage the engaging tabs from the tool body.
However, in order to remove the adjusting device of Japanese Utility Model Registration No. 2510156, it is necessary to rotate the operation sleeve by several times for disengaging the threaded portions from each other. Therefore, the removing and mounting operations take much time and there has been a problem that the operability is not good. In addition, because the removing operation is troublesome, an operation for loosening screws cannot be rapidly performed. Thus, it is necessary to remove the adjusting device in order to perform the screw loosening operation.
In case of the arrangement of U.S. Pat. No. 6,758,116, there is a backlash between the adjusting device and the tool body within a range of resilient deformation of the resilient hinges. Therefore, it is difficult to reliably hold the adjusting device against the tool body.
Thus, there is a need in the art for a working depth adjusting device that can be easily mounted to and removed from a tool body and can be reliably held against the tool body.